I've had two Petrol (or Gasoline for you Yanks
). powered bikes, The first was a swap meet special bought for $50. it had a large two stroke engine that was on a pivot. You pulled and locked up a lever near your left leg, as the lever came up, the engine (with a knurled direct drive extension) went down onto the top of the tyre. no clutch .. just down to idle when you wanted to stop and stall it on the brake.. and roll start it to get going.. not real sophisticated and never tried it in the city.. but it was good for around 25 miles per hour.. and very handy for a while..
I replaced it with a "Rotary Cycle" another 2 stroke engined bike.. a straight copy of the Sachs they ran a 100:1 fuel / oil mix, wouldn't call it fumey at all. and super quiet.. it was the closest thing to an "in hub" wheel you could get.. the engine sitting under the left side of the frame.
(Link Removed - No Longer Exists)
you should be able to see what it looks like in the link. the engine and unique rear wheel are integrated.. The only issue it ever had was the back wheel would come out of true.. as it was cast alloy, it had to be replaced..
the bike was a very good thing.. around one litre (one quart) of fuel would take me around 100km (60 miles) the one great advantage that petrol has over electric in my opinion.. it was limited to 200watts output as it the law in NSW Australia... and was good for just under 30 kph ...
The state government has since outlawed all petrol powered bikes because of the number of extremely powerful kits coming from China.. so even though mine complied with the law.. its still illegal.
after the Rotary Cycle I bought a used Chinese Electric scooter 24 volt with two separate sets of SLA batteries. You may laugh, but for what it was, it was very good, a solid well built machine.. (I'm pretty heavy .. around 280 pounds) and it was the one bike that never had an issue with buckled rims.. range wasn't fantastic however.. again, even though it conformed to every rule, our state government banned them, "because they look too much like a motorcycle" You don't know how good you have it in the states..